From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:38019) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UcFNR-0007v9-Jo for qemu-devel@nongnu.org; Tue, 14 May 2013 09:34:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UcFNP-0004t6-Ip for qemu-devel@nongnu.org; Tue, 14 May 2013 09:34:49 -0400 Received: from mail-ob0-x22c.google.com ([2607:f8b0:4003:c01::22c]:40528) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UcFNP-0004su-Cv for qemu-devel@nongnu.org; Tue, 14 May 2013 09:34:47 -0400 Received: by mail-ob0-f172.google.com with SMTP id tb18so549145obb.31 for ; Tue, 14 May 2013 06:34:46 -0700 (PDT) From: Anthony Liguori In-Reply-To: <20130514115838.GA24176@redhat.com> References: <87sj1qboo4.fsf@codemonkey.ws> <20130514115838.GA24176@redhat.com> Date: Tue, 14 May 2013 08:34:43 -0500 Message-ID: <87ppwt1y8c.fsf@codemonkey.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Subject: Re: [Qemu-devel] [PATCH RFC 00/13] qemu: generate acpi tables for the guest List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: seabios@seabios.org, lersek@redhat.com, qemu-devel@nongnu.org "Michael S. Tsirkin" writes: > On Mon, May 13, 2013 at 03:38:51PM -0500, Anthony Liguori wrote: >> I don't think it's a good idea to move BIOS functionality in QEMU. > > Just to clarify: generating ACPI tables is not BIOS > functionality. It ended up in seabios for historical > reasons. > > A normal scenario for ACPI tables is that they are written > in ASL and compiled with IASL. I wouldn't call this the normal scenario. Some tables are static but more tables are dynamic than you'd think. If you're a firmware engineer and you have to support dozens of platforms, it's much easier to make the tables dynamic than attempt to maintain dozens of ASL descriptions. A lot of what you'd consider to be static is actually dynamic in a multi-node system. > The tables are then stored > in some ROM device - most of them, except FACP, can actually > be mapped directly from ROM if necessary. > > You won't normally find real BIOS probing PCI slots for > hotplug support and writing EJ0 methods dynamically - > instead the assumption is that hardware (in this case QEMU) > supplies its own static description in form of ACPI tables. Actually, this is a very good example. In more modern boxes like Flex, there's a PCI-Express backplane that all of the nodes are connected to with a common set of slots for all nodes. You can configure in firmware how the slots map to each node. I can share an acpi dump from one of these systems when after I head into the office this morning. This is what's nice about a switched PCI complex. You have tremendous amounts of flexibility in how you set things up. Regards, Anthony Liguori > My patchset uses FW_CFG as such a ROM device. It would be > easy to switch to something else instead of FW_CFG. > Is this what you are suggesting? > > -- > MST